The present invention relates to a process for producing nitriles. More particularly, it relates to an improved method for producing nitriles by using an alkane as starting material.
Nitriles such as acrylonitrile and methacrylonitrile have been industrially produced as an important intermediate for the preparation of fibers, synthetic resins, synthetic rubbers and the like. The most popular method for producing such nitriles is to subject an olefin such as propylene, isobutene or the like to a catalytic reaction with ammcnia and oxygen in the presence of a catalyst in a gaseous phase at a high temperature.
More recently, there have been proposed methods for producing acrylonitrile or methacrylonitrile by using the so-called ammoxidation process, according to which a lower alkane such as propane, isobutane, etc., is subjected to a catalytic reaction with ammonia and oxygen in the presence of a catalyst in a gaseous phase. For instance, a method using an Mo type catalyst (Japanese Patent Application Laid-Open (KOKAI) Nos. 48-16887 (1973), 47-13312 (1972) (corresponding to GB 1,333,639), and 47-13313 (1972) (corresponding to USP 3,833,638) and Japanese Patent Publication No. 55-42071 (1980)), a method using V type catalyst (Jpn. Pat. Appln. Laid-Open (KOKAI) Nos. 47-33783 (1972) and 52-148022 (1977), Jpn. Pat. Pub. Nos. 50-23016 (1975) (corresponding to GB 1,336,135 and GB 1,336,136) and 47-51331 (1972) (corresponding to USP 3,433,823)), a method using Sb type catalyst (Jpn. Pat. Pub. Nos. 45-4733 (1970) (corresponding to GB 1,194,855), 47-14371 (1972) (corresponding to USP 3,670,008, USP 3,678,090 and USP 3,816,506), 50-17046 (1975) (corresponding to USP 3,670,006, USP 3,686,267 and USP 3,743,527), 50-28940 (1975) (corresponding to GB 1,334,859), 56-47901 (1981), and USP 3,686,295), and a method using other types of catalyst (Jpn. Pat. Pub. No. 50-16775 (1975) (corresponding ,to USP 3,652,638)) are known, but none of these known methods is satisfactory in selectivity of the objective nitriles.
In order to improve the selectivity of nitriles, it has been attempted to add a small quantity of an organic halide, inorganic halide or sulfur compound to the reaction system or to add water to the reaction system. However, the former method has a problem of possible corrosion of a reaction apparatus while the latter method involves a problem of formation of by-products by a side reaction.
Further, the methods using the conventional catalysts require a very high reaction temperature, which is about 500.degree. C. or higher, so that such methods are disadvantageous in terms of reactor material, production cost, etc.
The present inventors have made extensive researches on the method of producing nitriles by using an alkane as starting material and, as a result, found that by using a specific complex catalyst it was possible to produce the objective nitriles with a higher selectivity than attainable with the conventional methods, with no need of introducing a halide or water into the reaction system and at a lower temperature (about 380 to 480.degree. C.) than required in the conventional methods. The present invention was attained on the basis of such finding.